Modified wet tip antenna design

ABSTRACT

A microwave antenna including a feedline, a radiating section, an inflow hypotube, a puck, a transition collar and a sleeve. The feedline includes a coaxial cable including an inner and outer conductor, and a dielectric disposed therebetween. The radiating section includes a dipole antenna coupled to the feedline and a trocar coupled to the distal end of the dipole antenna. The inflow hypotube is disposed around the outer conductor and configured to supply fluid to the radiating portion. The puck includes at least two ribs with inflow slots defined between two adjacent ribs. The transition collar is coupled to the distal end of the inflow hypotube and the first end of the puck. The transition collar includes at least two outflow slots configured to receive fluid from a distal end of the inflow hypotube and to transition the fluid from the outflow slots to a distal end of the radiating section. The sleeve overlays the two outflow slots of the transition collar, the puck and at least the distal portion of the radiating section. The sleeve forms a fluid-tight seal with the transition collar proximal the outflow slots and defines a first gap for transitioning the fluid to exit the outflow slots of the transition collar to the distal end of the radiating section.

BACKGROUND

1. Technical Field

The present disclosure relates generally to microwave applicators usedin tissue ablation procedures. More particularly, the present disclosureis directed to a modified version of a choked wet-tip ablation antenna.

2. Background of Related Art

Treatment of certain diseases requires destruction of malignant tissuegrowths (e.g., tumors). It is known that tumor cells denature atelevated temperatures that are slightly lower than temperaturesinjurious to surrounding healthy cells. Therefore, known treatmentmethods, such as hyperthermia therapy, heat tumor cells to temperaturesabove 41° C., while maintaining adjacent healthy cells at lowertemperatures to avoid irreversible cell damage. Such methods involveapplying electromagnetic radiation to heat tissue and include ablationand coagulation of tissue. In particular, microwave energy is used tocoagulate and/or ablate tissue to denature or kill the cancerous cells.

Microwave energy is applied via microwave ablation antennas thatpenetrate tissue to reach tumors. There are several types of microwaveantennas, such as monopole and dipole. In monopole and dipole antennas,microwave energy radiates perpendicularly from the axis of theconductor. A monopole antenna includes a single, elongated microwaveconductor. Dipole antennas typically have a coaxial constructionincluding an inner conductor and an outer conductor separated by adielectric portion. More specifically, dipole microwave antennas includea long, thin inner conductor that extends along a longitudinal axis ofthe antenna and is surrounded by an outer conductor. In certainvariations, a portion or portions of the outer conductor may beselectively removed to provide for more effective outward radiation ofenergy. This type of microwave antenna construction is typicallyreferred to as a “leaky waveguide” or “leaky coaxial” antenna.

A typical tissue-penetrating (i.e., percutaneously inserted) microwaveenergy delivery device includes a transmission portion formed by a long,thin inner conductor that extends along the axis of the device. Theinner conductor is surrounded by a dielectric material and the outerconductor is radially-disposed relative to the dielectric material andforms a coaxial waveguide for transmitting a microwave signal. Thedistal end of the transmission portion of the outer conductor connectsto a microwave antenna configured to receive the microwave signal fromthe transmission portion and to radiate the microwave energy signal totissue.

Structural strength is provided to the microwave energy delivery deviceby surrounding at least part of the transmission portion and/or themicrowave antenna with a high-strength jacket. The distal end of thehigh-strength jacket may connect to, or form, a sharpened tip forpiercing tissue.

Invasive procedures have been developed in which the microwave antennadelivery device is inserted directly into a point of treatment viapercutaneous insertion. Such invasive procedures potentially providebetter temperature control of the tissue being treated. Because of thesmall difference between the temperature required for denaturingmalignant cells and the temperature injurious to healthy cells, a knownheating pattern and predictable temperature control is important so thatheating is confined to the tissue to be treated. For instance,hyperthermia treatment at the threshold temperature of about 41.5° C.generally has little effect on most malignant growths of cells. However,at slightly elevated temperatures above the approximate range of 43° C.to 45° C., thermal damage to most types of normal cells is routinelyobserved; accordingly, great care must be taken not to exceed thesetemperatures in healthy tissue.

Systems and methods developed to control heating and prevent elevatedtemperatures to surrounding tissue typically include cooling fluid thatcirculates around at least a portion of the microwave energy deliverydevice. For example, in one system cooling fluid is provided to thedistal end of the microwave energy delivery device via a thin-walledtube. The thin-walled tube deposits the cooling fluid near the microwaveantenna and the cooling fluid flows proximally through a return path inthe microwave energy deliver device.

There are several challenges to providing cooling to a microwave energydelivery device. The first challenge is providing suitable supply andreturn fluid pathways in the microwave energy delivery device withoutincreasing the overall diameter of the microwave energy delivery device.Another challenge is providing suitable supply and return fluid pathwayswhile maintaining a concentric configuration throughout the microwaveenergy delivery device. Yet another challenge is providing a suitableconfiguration that simplifies assembly and manufacturing.

SUMMARY

The microwave energy delivery devices described hereinbelow includes anassembly that forms a fluid-cooled device with a substantiallyconcentric geometry along the length of the device without increasing inthe overall diameter of the microwave energy delivery device.

An apparatus and method of fabricating a microwave energy deliverydevice, which is structurally robust enough for unaided direct insertioninto tissue is described herein. The microwave antenna is generallycomprised of a radiating portion which may be connected to a feedline(or shaft), which in turn, may be connected by a cable to a powergenerating source such as a generator. The microwave assembly may be amonopole microwave energy delivery device but is preferably a dipoleassembly. The distal portion of the radiating portion preferably has atapered end which terminates at a tip to allow for the direct insertioninto tissue with minimal resistance. The proximal portion is locatedproximally of the distal portion.

The adequate rigidity necessary for unaided direct insertion of theantenna assembly into tissue, e.g., percutaneously, while maintaining aminimal wall thickness of less than 0.010 inches of an outer jacket,comes in part by a variety of different designs. An embodiment of amicrowave design includes a coaxial cable. The coaxial cable includes aninner conductor, an outer conductor, and a dielectric insulator disposedtherebetween. The radiating section includes a dipole antenna that iscoupled to the feedline and a trocar coupled to the dipole antenna at adistal end thereof. The microwave antenna further includes an inflowhypotube disposed around the outer conductor. The inflow hypotubesupplies fluid to the radiating portion. The inflow hypotube enables theincreased in strength thereby allowing for a smaller wall thicknessrequirement of the outer jacket of a microwave antenna.

In one embodiment, the microwave antenna includes a feedline, aradiating section, an inflow hypotube, a puck, a transition collar and asleeve. The feedline includes a coaxial cable with an inner conductor,an outer conductor, and a dielectric disposed therebetween. Theradiating section includes a dipole antenna coupled to the feedline anda trocar coupled to the distal end of the dipole antenna. The inflowhypotube is disposed around the outer conductor and configured to supplyfluid to the radiating portion. The puck includes two or more ribsextending from the first end to the second end. The ribs define inflowslots between two adjacent ribs. The transition collar is coupled to thedistal end of the inflow hypotube and the puck includes at least twooutflow slots at the proximal end. The transition collar is configuredto receive fluid from a distal end of the inflow hypotube and transitionthe fluid from the outflow slots to a distal end of the radiatingsection. The sleeve overlays the outflow slots of the transition collar,the puck and at least the distal portion of the radiating section. Thesleeve forms a first fluid-tight seal with the transition collar,proximal the outflow slots, and defines a first gap for transitioningthe fluid to exit the outflow slots of the transition collar to thedistal end of the radiating section. The sleeve may be a polyimidesleeve.

The microwave antenna may further include an outer jacket that surroundsthe proximal to distal end of the feedline and an outer hypotube. Theouter jacket forms a fluid-tight seal with the trocar and/or the distalend of radiating section and defines a second gap for receiving fluidfrom the first gap. The outer hypotube surrounds the inflow hypotube atthe proximal end of the feedline and defines a third gap positionedrelative to the inflow hypotube. The outer hypotube includes one or moreslots defined therein and forms a fluid-tight seal with the outer jacketproximal one or more slots. The one or more slots are configured toenable the fluid to flow proximally from the second gap into the thirdgap and through the microwave antenna.

In another embodiment, the inflow hypotube and/or the outer hypotube aremade from stainless steel or from a non-metallic composite such asPolyMed® made by Polygon. The wall thickness of the outer hypotube andthe inflow hypotube may be less than about 0.010 inches. The microwaveantenna may further include a choke configured to partially surround aproximate portion of the feedline

In yet another embodiment, the puck is injection molded during themanufacturing process to form a water-tight seal around the outerconductor. The transition collar may be press-fit over the inflowhypotube to form a fluid-tight seal therebetween.

In a further embodiment, the microwave antenna may included a connectionhub with a cable connector coupled to the feedline, an inlet fluid portand an outlet fluid port defined therein and a bypass tube configured totransition fluid proximate the cable connector to the outlet fluid port.An inflow tube may be coupled to the inlet fluid port for supplying thefluid thereto and an outflow tube may be coupled to the outlet fluidport and in fluid communication with the inflow hypotube for withdrawingfluid therefrom.

A method for manufacturing a microwave antenna is also disclosed hereinand may include the steps of: providing a feedline including a coaxialcable including an inner conductor, an outer conductor, and a dielectricdisposed therebetween; coupling a radiating section to the distal end ofthe feedline, the radiating section including a dipole antenna; couplinga trocar to the distal end of the dipole antenna; disposing an inflowhypotube around the outer conductor, the inflow hypotube configured tosupply fluid to the radiating section; disposing a puck around at leasta portion of the radiating section having a distal end and a proximalend, the puck including two or more longitudinal ribs for providingmechanical strength to the microwave antenna, the two or more ribsextending from the distal end to the proximal end to define inflow slotsbetween two adjacent ribs; disposing a transition collar between adistal end of the inflow hypotube and a proximal end of the puck, thetransition collar including at least two outflow slots configured toreceive fluid from a distal end of the inflow hypotube and transitionthe fluid from the at least two outflow slots to a distal end of theradiating section; and disposing a sleeve to overlay the at least twooutflow slots of the transition collar, the puck and at least the distalportion of the radiating section, the sleeve forming a fluid-tight sealwith the transition collar proximal the at least two outflow slots anddefining a first gap for transitioning the fluid to exit the at leasttwo outflow slots of the transition collar to the distal end of theradiating section.

The method for manufacture may further include the steps of: disposingan outer jacket radially outward of the distal end of the feedline, theouter jacket forming a fluid-tight seal with one of the trocar and adistal end of the radiating section, the outer jacket defining a secondgap for receiving fluid from the first gap; and disposing an outerhypotube radially outward of the inflow hypotube and defining a thirdgap positioned relative to the inflow hypotube, the outer hypotubeincluding at least one slot defined therein and forming a fluid-tightseal with the outer jacket proximal the at least one slot, the at leastone slot configured to enable the fluid to flow proximally from thesecond gap into the third gap and through the microwave antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a schematic diagram of a microwave ablation system accordingto an embodiment of the present disclosure;

FIG. 2 is an isometric view of a distal portion of the microwave energydelivery device according to one embodiment of the present disclosure;

FIG. 3A is a longitudinal cross-sectional view of the feedline portionof the microwave energy delivery device of FIG. 2;

FIG. 3B is a traverse, cross-sectional view taken along line 3B-3B ofFIG. 2;

FIG. 4 is a perspective view of the distal portion of the microwaveenergy delivery device illustrating the coaxial inflow and outflowchannels according to the present disclosure;

FIG. 5 is an exploded view of the distal portion of the microwave energydelivery device illustrated in FIG. 4;

FIG. 6 is a longitudinal cross-sectional view of the distal tip of themicrowave energy delivery device.

FIG. 7A is a transverse, cross-sectional view of the distal tip of themicrowave energy delivery device according to one embodiment of thepresent disclosure;

FIG. 7B is a transverse, cross-sectional view of the distal tip of themicrowave energy delivery device according to another embodiment of thepresent disclosure; and

FIG. 8 is a perspective view of the distal portion of the microwaveenergy delivery device illustrating the coaxial outflow channelaccording to the present disclosure;

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are described hereinbelow with reference to the accompanying drawings. In the followingdescription, well-known functions or constructions are not described indetail to avoid obscuring the present disclosure in unnecessary detail.

FIG. 1 illustrates a microwave ablation system 10 that includes amicrowave energy delivery device 12, a microwave generator 14 and acooling fluid supply 33. The microwave energy delivery device 12 iscoupled to a microwave generator 14 via a flexible coaxial cable 16 andcoupled to the cooling fluid supply 33 via cooling fluid supply lines 86and 88. Cooling fluid exits the microwave energy delivery device 12through a cooling fluid return line 88 and is discharged in a suitabledrain. In a closed-loop cooling fluid system the microwave energydelivery device 12 couples to the cooling fluid supply 33 via a coolingfluid return line 88 and cooling fluid is cycled through the coolingfluid supply 33. In an opened-loop cooling fluid system the coolingfluid return line 88 deposits the cooling fluid in a drain or othersuitable disposable receptacle and new cooling fluid is provided to thecooling fluids supply from a cooling fluid reservoir 36 or othersuitable source of cooling fluid.

Microwave energy delivery device 12 generally includes a connection hub22, a feedline 20 and a radiating portion 18. Connection hub 22 connectsthe microwave generator 14 and the cooling fluid supply 33 to themicrowave energy delivery device 12. The microwave signal is produced bythe microwave generator 14, transmitted through the flexible coaxialcable 16, which connects to the connection hub 22, and the connectionhub 22 facilitates the transfer of the microwave energy signal to thefeedline 20. Connection hub 22 further facilitates the transfer ofcooling fluid to and from the feedline 20. Cooling fluid, provided fromthe pump 34 of the cooling fluid supply 33, is provided to theconnection hub 22 through the cooling fluid supply line 86. Connectionhub 22 transfers the cooling fluid from the cooling fluid supply line 86to the cooling fluid supply lumen (not explicitly shown) of the feedline20. Cooling fluid, after being circulated through the feedline 20 andradiating portion 18 of the microwave energy delivery device 12, isreturned to the connection hub 22 through the return lumen (notexplicitly shown) of the feedline 20. Connection hub 22 facilitates thetransfer of the cooling fluid from the return lumen (not explicitlyshown) to the cooling fluid return line 88.

In one embodiment, the microwave ablation system 10 includes aclosed-loop cooling system wherein the cooling fluid return line 88returns the cooling fluid to the pump 34 of the cooling fluid supply 33.The cooling fluid supply 33 cools the returned cooling fluid from thecooling fluid return line 88 before recirculating at least a portion ofthe returned cooling fluid through the Microwave ablation system 10.

In another embodiment, the cooling fluid return line 88 connects to asuitable drain and/or reservoir (e.g., cooling fluid from the microwaveenergy delivery device 12 is not returned to the cooling fluid supply33). Cooling fluid reservoir 36 of the cooling fluid supply 33 providesa continuous supply of cooling fluid to the pump 34. Cooling fluidreservoir 36 may also include a temperature control system configured tomaintain the cooling fluid at a predetermined temperature. Coolant fluidmay include any suitable liquid or gas, including air, or anycombination thereof.

The microwave energy delivery device 12 may include any suitablemicrowave antenna 40 such as, for example, a dipole antenna, a monopoleantenna and/or a helical antenna. The microwave generator 14 may beconfigured to provide any suitable microwave energy signal within anoperational frequency from about 300 MHz to about 10 GHz. The physicallength of the microwave antenna 40 is dependant on the frequency of themicrowave energy signal generated by the microwave generator 14. Forexample, in one embodiment, a microwave generator 14 providing amicrowave energy signal at about 915 MHz drives a microwave energydelivery device 12 that includes a microwave antenna 40 with a physicallength of about 1.6 cm to about 4.0 cm.

FIG. 2 is an enlarged view of the distal portion of the microwave energydelivery device 12 of FIG. 1 and includes a feedline 20, a proximalradiating portion 42 and a distal radiating portion 44. The proximalradiating portion 42 and the distal radiating portion 44 form a dipolemicrowave antenna 40. As illustrated in FIG. 2, proximal radiatingportion 42 and the distal radiating portion 44 are unequal therebyforming an unbalanced dipole antenna 40. The microwave energy deliverydevice 12 includes a sharpened tip 48 having a tapered end 24 thatterminates, in one embodiment, at a pointed end 26 to allow forinsertion into tissue with minimal resistance at a distal end of theradiating portion 18. In another embodiment the radiating portion 18 isinserted into a pre-existing opening or catheter and the tip may berounded or flat.

Sharpened tip 48 may be machined from various stock rods to obtain adesired shape. The sharpened tip 48 may be attached to the distalradiating portion 44 using various adhesives or bonding agents, such asan epoxy sealant. If the sharpened tip 48 is metal, the sharpened tip 48may be soldered to the distal radiating portion 44 and may radiateelectrosurgical energy. In another embodiment, the sharpened tip 48 anda distal radiating portion 44 may be machined as one piece. Thesharpened tip 48 may be formed from a variety of heat-resistantmaterials suitable for penetrating tissue, such as ceramic, metals(e.g., stainless steel) and various thermoplastic materials, such aspolyetherimide, polyimide thermoplastic resins, an example of which isUltem® sold by General Electric Co. of Fairfield, Conn.

FIG. 3A is a longitudinal cross-sectional view of a section of thefeedline 20 of the microwave energy delivery device 12 of FIG. 1 andFIG. 3B is a transverse, cross-sectional view of the feedline 20 of themicrowave energy delivery device 12 of FIG. 3A. Feedline 20 is coaxiallyformed with an inner conductor 50 at the radial center surrounded by adielectric layer 52 and an outer conductor 56. Inflow hypotube 55 isspaced apart and disposed radially outward from the outer conductor 56.The outer surface of the outer conductor 56 b and the inner surface ofthe inflow hypotube 55 a form an inflow channel 17 i allowing coolingfluid to flow distally through the feedline 20 of the microwave energydelivery device 12 as indicated by cooling fluid inflow arrows 17 i. Theinflow hypotube 55 may be formed from a variety of heat-resistantmaterials, such as ceramic, metals (e.g., stainless steel), variousthermoplastic materials, such as polyetherimide, polyimide thermoplasticresins, an example of which is Ultem® sold by General Electric Co. ofFairfield, Conn., or composite medical tubing, an example of which isPolyMed sold by Polygon of Walkerton, Ind. In one embodiment, the inflowhypotube 55 may have a wall thickness less than about 0.010 inches. Inanother embodiment, the inflow hypotube 55 may have a wall thicknessless than about 0.001 inches.

The outer hypotube 57 is spaced apart from, and radially outward from,the inflow hypotube 55. The outer surface of the inflow hypotube 55 band the inner surface of the outer hypotube 57 a form an outflow channel17 o that allows cooling fluid to flow proximately through the feedline20 of the microwave energy delivery device 12 as indicated by coolingfluid outflow arrows 17 o. The outer hypotube 57 may be formed from avariety of heat-resistant materials, such as ceramic, metals (e.g.,stainless steel), various thermoplastic materials, such aspolyetherimide, polyimide thermoplastic resins, an example of which isUltem® sold by General Electric Co. of Fairfield, Conn., or compositemedical tubing, an example of which is PolyMed sold by Polygon ofWalkerton, Ind. In one embodiment, the outer hypotube 57 may have a wallthickness less than about 0.010 inches. In another embodiment, the outerhypotube 57 may have a wall thickness less than about 0.001 inches.

The substantially radially concentric cross-sectional profile, asillustrated in FIG. 3B, provides uniform flow of fluid in both theinflow channel 17 i and the outflow channel 17 o. For example, an inflowchannel gap G1 defined between the outer surface of the outer conductor56 b and the inner surface of the inflow hypotube 55 a is substantiallyuniform around the circumference of the outer conductor 56. Similarly,an outflow channel gap G2 defined between the outer surface of theinflow hypotube 55 b and the inner surface of the outer hypotube 57 issubstantially uniform around the circumference of the inflow hypotube55.

In addition, the cross-sectional area of the inflow channel 17 i and theoutflow channel 17 o (i.e., the effective area of each channel in whichfluid flows) is the difference between the area at the outer surface ofeach channels 17 i, 17 o (i.e., the area at the inner diameter of theinflow hypotube 55 and the area at the inner diameter of the outerhypotube 57, respectively) and the area at the inner surface of the eachchannels 17 i, 17 o (i.e., the area at the outer diameter of the outerconductor 56 and the area at the outer diameter of the inflow hypotube55). The cross-sectional area of the inflow channel 17 i and the outflowchannel 17 o is substantially uniform along the longitudinal length ofthe feedline 20. In addition, transverse shifting of the inflow hypotube55 within the outer hypotube 57 or transverse shifting of the outerconductor 56 within the inflow hypotube 55, may create a non-uniforminflow or outflow channel gap G1, G2, but will not affect thecross-sectional area of either inflow channel 17 i and/or outflowchannel 17 o.

FIG. 4 (illustrating in partial assembly the radiating portion 18 ofFIG. 1) further illustrates the inflow fluid flow pathways. Theradiating portion 18 is formed by inserting the distal portion of thefeedline 20 into the microwave antenna 40.

The feedline 20 is configured to provide cooling fluid and a microwaveenergy signal to the microwave antenna 40. As discussed hereinabove, thefeedline 20 provides cooling fluid through the inflow channel 17 iformed between the inflow hypotube 55 and the outer conductor 56 of thefeedline 20. The feedline 20 also provides a microwave energy signalbetween the inner conductor 50 and the outer conductor 56.

The microwave antenna 40 includes a tapered inflow transition collar 53,a channeled puck 46, a distal radiating portion 44, including aplurality of antenna sleeve stops 68 a-68 d, and a sharpened tip 48. Thefeedline 20, when inserted into the microwave antenna 40, connects theouter conductor 56 to the tapered inflow transition collar 53 and theinner conductor 50 to the distal radiating portion 44.

FIG. 5 is an exploded view of the microwave antenna 40 of FIG. 4 thatfurther illustrates the components of the microwave assembly. Thetapered inflow transition collar 53 includes an outer taper 60 a, amiddle taper 60 b and an inner taper 60 c and is configured totransition the cooling fluid from the inflow channel 17 i to variousfluid channels formed in the microwave antenna 40 as discussedhereinbelow. During assembly, and as illustrated in FIG. 4 and discussedhereinbelow, the distal end of the feedline 20 is inserted into theproximal end of the tapered inflow transition collar 53. Each component50, 52, 55, 56 of the feedline 20 is cut to a specific length such thatwhen the feedline 20 is inserted each component ends at a predeterminedposition within the microwave antenna assembly 40.

Starting with the radially-outward component of the distal end of thefeedline 20, the inflow hypotube 55 (See FIG. 4) is inserted into theproximal end of the outer taper 60 a portion of the tapered inflowtransition collar 53. The transition between the outer taper 60 a andthe middle taper 60 b forms a mechanical stop for the inflow hypotube55. Outer taper 60 a and inflow hypotube 55 forms a fluid-tight sealtherebetween thereby limiting cooling fluid to the middle taper 60 b ofthe tapered inflow transition collar 53. The fluid-tight seal betweenthe inflow hypotube 55 and the outer taper 60 a may be formed byadhesive, epoxy, or a polytetrafluoroethylene or other suitable sealant,or fluid-tight seal may be formed by a tight mechanical connectionbetween the inflow hypotube 55 and the outer taper 60 a.

In one embodiment, the inflow hypotube 55 is formed of a conductivemetal such as, for example, stainless steel, steel, copper or any othersuitable metal, and the fluid-tight seal insulates the inflow hypotube55 and the inner surface of the tapered inflow transition collar 53. Inanother embodiment, the fluid tight seal may include one or moreinsulating materials that forms a dielectric barrier between the inflowhypotube 55 and tapered inflow transition collar 53.

The outer conductor 56 when inserted into the proximal end of the outertaper 60 a extends through the middle taper 60 b with at least a portionof the outer conductor 56 connecting to the inner taper 60 c. The outerconductor 56 and inner taper 60 c form an electrical connectiontherebetween such that microwave energy signal provided by the outerconductor 56 conducts to the tapered inflow transition collar 53 suchthat the tapered inflow transition collar 53 forms at least a portion ofthe proximal radiating portion 42 of the microwave antenna 40.

The outer surface of the inflow hypotube 55 and the inner surface of theouter taper 60 a form a fluid-tight seal therebetween, Fluid exits theinflow channel 17 i and is deposited in the open area formed within themiddle taper 60 b. The outer surface of the outer conductor 56 and innersurface of the inner taper 60 c form a fluid-tight seal therebetween,thereby preventing the cooling fluid from traveling distal of the middletaper 60 b within the tapered inflow transition collar 53.

In one embodiment, an electrical connection is formed between the outerconductor 56 and the inner taper 60 c of the tapered inflow transitioncollar 53. As such, tapered inflow transition collar 53 forms at least aportion of the proximal radiating portion 42 of the radiating portion18, wherein the radiating portion 18 is a dipole antenna. The electricalconnection between the outer conductor 56 and the inner taper 60 c mayinclude all of the contact surface therebetween or the electricalconnection may include only a portion thereof. For example, in oneembodiment the electrical connection between the outer conductor 56 andthe inner taper 60 c is formed circumferentially along the distalportion of the inner taper 60 c and the remaining portion of the contactsurface insulates the outer conductor 56 and the inner taper 60 c.

In another embodiment, the fluid-tight seal between the outer conductor56 and the inner taper 60 c forms an insulating barrier therebetween andthe tapered inflow transition collar 53 does not form a portion of theradiating portion 18, wherein the radiating portion 18 is a monopolarantenna.

In yet another embodiment, the fluid-tight seal between the outerconductor 56 and the inner taper 60 c forms an insulating barriertherebetween. An electrical connection between the outer conductor 56and the inner taper 60 e is formed by connecting a distal end of theouter conductor 56 or the inner taper 60 e to one another.

The fluid-tight seal between the inflow hypotube 55 and the outer taper60 a and the fluid-tight seal between the outer conductor 56 and theinner taper 60 c isolates the cooling fluid discharged from the inflowchannel 17 i to the middle taper 60 b of the tapered inflow transitioncollar 53. As additional fluid is deposited in the middle taper 60 b,pressure builds and the cooling fluid exits the middle taper 60 bthrough one of the plurality of cooling fluid transition apertures 53a-53 d formed in the tapered inflow transition collar 53.

After the cooling fluid flows radially outward through one of theplurality of cooling fluid transition apertures 53 a-53 d formed in themiddle taper 60 b, the cooling fluid flows distally along the outersurface of the middle taper 60 b between the tapered inflow transitioncollar 53 and the antenna sleeve 2. Antenna sleeve 2 forms a fluid-tightseal with the outer taper 60 a of the tapered inflow transition collar53 thereby requiring fluid to flow distally toward the channeled puck46. In one embodiment, the antenna sleeve 2 is a thin polyimide sleeve,or other suitable non-conductive material that has little or no impacton the transmission and/or delivery of microwave radiation.

With reference to FIG. 4, cooling fluid exiting one of the plurality ofcooling fluid transition apertures 53 a-53 d flows distally along theouter surface of the tapered inflow transition collar 53, the outersurface of the channeled puck 46 and the outer surface of the distalradiating portion 44 and along the inner surface of the antenna sleeve2. Proximal end of antenna sleeve 2 forms a fluid-tight seal with theouter taper 60 a of the tapered inflow transition collar 53. In oneembodiment, the proximal end 2 a of the antenna sleeve 2 mates with aproximal antenna sleeve stop 53 s formed in the outer taper 60 a suchthat the outer diameter of the antenna sleeve 2 and the outer diameterof the outer taper 60 a are substantially identical.

A channel 67 a, 67 b, 67 c, 67 d is formed between each of the adjacentraised portions 66 a-66 d wherein the radial outer surface of thechanneled puck 46 at the raised portion 66 a-66 d is radially outwardfrom the outer surface of the channeled puck 46 at each of the channels67 a-67 d. Channels 67 a-67 d are configured to form a cooling fluidpathway between the outer surface of the channeled puck 46 and the innersurface of the antenna sleeve 2.

As illustrated in FIG. 4, cooling fluid exits the middle taper 60 b ofthe tapered inflow transition collar 53, flows distal through theplurality of channels 67 a-67 d formed between the raised portions 66a-66 d of the channeled puck 46 and the antenna sleeve 2 and isdeposited on the outer surface of the distal radiating portion 44. Thecooling fluid is deposited into a gap formed between the outer surfaceof the proximal end 2 a of the distal radiating portion 44 and the innersurface of the antenna sleeve 2.

Distal end 2 b of the distal radiating portion 44 includes a pluralityof antenna sleeve stops 68 a-68 d. Adjacent antenna sleeve stops 68 a-68d are spaced apart from each other and form a plurality of distal flowchannels 70 a-70 d therebetween. Distal end 2 b of antenna sleeve 2 isconfigured to abut a distal lip 69 a-69 d formed on the distal end ofeach of the respective antenna sleeve stops 68 a-68 d.

Fully assembled, the distal end of the outer jacket 43 forms a fluidtight seal with a proximal portion of the sharpened tip 48. Asillustrated in FIG. 6, a fluid-tight seal is formed between the outerjacket 43 and the sharpened tip 48, wherein the fluid-tight seal isdistal the distal end 2 b of the antenna sleeve 2. As such, the antennasleeve 2 is contained within the outer jacket 43 and at least a portionof the outflow channel 17 o is formed between the inner surface of theouter jacket 43 and the outer surface of the antenna sleeve 2.

In one embodiment, the distal lip 69 a-69 d of the respective antennasleeve stops 68 a-68 d extend radially outward from the outer surface ofthe antenna sleeve 2 and space the outer jacket 43 from the outersurface of the antenna sleeve 2. A gap is formed between the antennasleeve 2 and the outer jacket 43 that forms at least a portion of theoutflow channel 17 o. The plurality of circumferentially-spaced sleevestops 68 a-68 d uniformly position the outer jacket 43 with respect tothe antenna sleeve 2.

FIG. 5 is an exploded view of a portion of the radiating portion 18illustrated in FIG. 4 including the tapered inflow transition collar 53,the channeled puck 46, the distal radiating portion 44, the antennasleeve 2 and the sharpened tip 48. Assembled, the channeled puck 46 ispositioned between the tapered inflow transition collar 53 and thedistal radiating portion 44. Similarly, the antenna sleeve 2 is alsopositioned between a portion of the tapered inflow transition collar 53and the distal radiating portion 44; the antenna sleeve 2 being spacedradially outward from the channeled puck 46.

As discussed hereinabove, the tapered inflow transition collar 53includes an outer taper 60 a, a middle taper 60 b and an inner taper 60c. A portion of the outer surface of the outer taper 60 a may form aproximal antenna sleeve stop 53 s configured to receive the proximal endof the antenna sleeve 2. Outer taper 60 a is configured to slide overthe distal end of the inflow hypotube 55. Inflow hypotube 55 may abutthe transition portion between the outer taper 60 a and the middle taper60 b. Fluid-tight seals, formed between the inflow hypotube 55 and theouter taper 60 a and between the outer conductor 56 and the inner taper60 c, force the cooling fluid traveling distally through in inflowchannel 17 i (formed between outer surface of the outer conductor 56 andthe inner surface of the inflow hypotube 55, see FIG. 3A) to bedeposited into the middle taper 60 b of the tapered inflow transitioncollar 53.

In one embodiment the fluid-tight seal between the tapered inflowtransition collar 53 and the inflow hypotube 55 is formed by a press-fitconnection therebetween. The inflow hypotube 55 may be press-fit overthe tapered inflow transition collar 53 or the tapered inflow transitioncollar 53 may be press-fit over the inflow hypotube 55, as illustratedin FIGS. 2, 4 and 8.

The outer diameters of the outer taper 60 a, a middle taper 60 b and aninner taper 60 c, D1, D2, D3, respectively, and the thickness of eachtaper 60 a-60 c are configured to facilitate the assembly of componentsthat form the microwave energy delivery device 12. For example, thediameter D1 and thickness of the outer taper 60 a is selected such thatthe inflow hypotube 55 forms a fluid-tight seal with the inner surfaceof the outer taper 60 a and the antenna sleeve 2 forms a fluid-tightseal with the outer diameter of the outer taper 60 a. The diameter D2 ofthe middle taper 60 b is selected to provide an adequate gap between theouter conductor 56 and the antenna sleeve 2 and to facilitate fluid flowthrough the middle taper 60 b. The diameter D3 and thickness of theinner taper 60 c is selected such that the outer conductor 56 forms afluid tight seal with the inner surface of the inner taper 60 c and thechanneled puck 46 forms a fluid-tight seal with the outer diameter ofthe inner taper 60 c.

The three tiers of the tapered inflow transition collar 53 areconfigured to facilitate the transition of cooling fluid between a firstportion of the inflow channel 17 i (radially formed in a first portionof the coaxially configured structure) and a second channel portion ofthe inflow channel 17 i (radially formed in a second portion of thecoaxially configured structure). For example (proximal to the taperedinflow transition collar 53), a first portion of the inflow channel 17 iis formed between the outer surface of the outer conductor 56 and theinner surface of the inflow hypotube 55 and at a point distal to thetapered inflow transition collar 53, a second portion of the inflowchannel 17 i is formed between the antenna sleeve 2 and the channeledpuck 46.

In another embodiment, the tapered inflow transition collar 53facilitates the transition of fluid from a first portion of the inflowchannel 17 i formed at a first radial distance from the radial center ofthe microwave energy delivery device 12 to a second portion of theinflow channel 17 i formed at a second radial distance from the radialcenter of the microwave energy delivery device 12. The first and secondradial distances from the radial center of the microwave energy deliverydevice 12 may or may not be equal.

The proximal end of the channeled puck 46 is configured to receive atleast a portion of the inner taper 60 c of the tapered inflow transitioncollar 53 and forms a fluid-tight seal therebetween and the distal endof the channeled puck 46 is configured to receive at least a portion ofthe distal radiating portion 44. The inner conductor (not explicitlyshown) extends through the radial center of the channeled puck 46 and isreceived by the distal radiating portion 44.

In one embodiment the channeled puck 46 is injection molded during themanufacturing process to form a water-tight seal around a portion of theouter conductor 56 and/or a portion of the tapered inflow transitioncollar 53. In another embodiment, the channeled puck 46 is press-fitover a portion of the outer conductor and/or a portion of the taperedinflow transition collar 53 and forms a fluid-tight seal therebetween.

The distal radiating portion 44 includes a conductive member that may beformed from any type of conductive material, such as metals (e.g.,copper, stainless steel, tin, and various alloys thereof). The distalradiating portion 44 may have a solid structure and may be formed fromsolid wire (e.g., 10 AWG). In another embodiment, the distal radiatingportion 44 may be formed from a hollow sleeve of an outer conductor 56of the coaxial cable or another cylindrical conductor. The cylindricalconductor may then be filled with solder to convert the cylinder into asolid shaft. More specifically, the solder may be heated to atemperature sufficient to liquefy the solder within the cylindricalconductor (e.g., 500° F.) thereby creating a solid shaft.

The radially-outward surface of the channeled puck 46 includes aplurality of raised portions 66 a-66 d and/or a plurality of recessedportions that form the channels 67 a-67 d. The plurality of raisedportions 66 a-66 d are configured to slideably engage the antenna sleeve2 and form a plurality of inflow channels 17 i defined between therecessed portions and the inner surface of the antenna sleeve 2.

Antenna sleeve 2 is configured to surround the channeled puck 46 andsurround at least a portion of the distal radiating portion 44. Asdiscussed hereinabove, the proximal end portion of the antenna sleeve 2connects to the proximal antenna sleeve stop 53 s (formed in a portionof the outer taper 60 a) and the distal end portion of the antennasleeve 2 connects to the distal antenna sleeve stops 68 a-68 d formed inthe distal radiating portion 44. A electrical connection between thedistal radiating portion 44 and the inner conductor (not explicitlyshown) may be formed through access slot 70. The access slot 70 may befilled with a suitable electrically conductive material and anelectrical connection may be formed between the distal radiating portion44 and the inner conductor (not explicitly shown). Distal end of thedistal radiating portion 44 may connect to sharpened tip 48 or may formthe sharpened tip 48.

The inflow channel 17 i and the outflow channel 17 o (i.e., the paths ofthe cooling fluid as it flows through the distal end of the microwaveenergy delivery device 12) are illustrated in FIGS. 4 and 6. Coolingfluid flows distally through the distal flow channels 70 a-70 d formedbetween adjacent antenna sleeve stops 68 a-68 d. After the cooling fluidflows distal of the distal end 2 b of the antenna sleeve 2, the fluid isdeposited in a fluid transition chamber 117 formed between the distalradiating portion 44 and the outer jacket 43. A fluid-tight seal, framedbetween the outer jacket 43 and the sharpened tip 48, prevents fluidfrom flowing distal the fluid transition chamber 117. As indicated bythe transition arrows cooling fluid in the fluid transition chamber 117exits the fluid transition chamber 117 and flows proximally and into theoutflow channel 17 o formed between the outer surface of the antennasleeve 2 and the inner surface of the outer jacket 43.

In another embodiment and as illustrated in FIGS. 7A-7B, the radiallyoutward portion of the distal lip 69 a-69 d formed on the distal end ofeach of the respective antenna sleeve stops 68 a-68 d (i.e., the portionof the distal lips 69 a-69 d that contact the outer jacket 43) may formadditional channels between the distal lips 69 a-69 d and the outerjacket 43 to allow the cooling fluid to flow proximally from the fluidtransition chamber 117.

The distal portion of the outflow channel 17 o is illustrated in FIG. 8.The outer jacket 43 forms the outer boundary of the outflow channel 170in the distal portion of the microwave energy delivery device 12. Thedistal end of the outer jacket 43 forms a fluid tight seal with thesharpened tip 48 and/or the distal radiating portion 44 and the proximalend forms a fluid tight seal with a portion of the outer hypotube 57proximal the fluid outflow slots 57 a, 57 b (57 c, 57 d not shown).Outer hypotube 57 may further include a proximal outer jacket stop 57 sthat provides a smooth transition on the outer surface of the microwaveenergy delivery device 12 between the outer hypotube 57 and the outerjacket.

A portion of the outflow channel 17 o is formed between the interiorsurface of the outer jacket 43 and at least a portion of the antennasleeve 2, a portion of the tapered inflow transition collar 53, aportion of the choke dielectric 19, a portion of the EMF shield 28 thatcovers the core choke (not shown) and a portion of the outer hypotube57. The coaxial arrangement of the outflow channel 17 o provides for theuniform application of cooling fluid to the distal portion of themicrowave energy delivery device 12.

On the proximal end of the outer jacket 43 the fluid-tight seal betweenthe outer jacket 43 and the outer hypotube 57 directs the cooling fluidto travel through the fluid outflow slots 57 a, 57 b (57 c, 57 d notexplicitly shown) and into the portion of the outflow channel 17 oformed between the interior surface of the outer hypotube 57 and theouter surface of the inflow hypotube 55, as illustrated in FIG. 3A anddescribed hereinabove.

As illustrated in FIGS. 1-8 and described hereinabove, the microwaveenergy delivery devices 12 includes a substantially coaxiallyarrangement through the length. Various layers of the microwave energydelivery device 12 form a substantially coaxial arrangement of theinflow channel 17 i and a substantially coaxial arrangement of theoutflow channel 17 o between two (or more) of the coaxial layers. Thesubstantially coaxial inflow and outflow channels 17 i, 17 o coaxiallydistribute the cooling fluid and thereby provides even coolingthroughout the microwave energy delivery device 12.

Various structures in the microwave energy delivery device 12 facilitatethe transition of the cooling fluid between the various sections of theinflow and outflow channels 17 i, 17 o respectively, while maintaining asubstantially coaxial arrangement throughout the device. The taperedinflow transition collar 53 transitions the cooling fluid from inflowchannel 17 i formed between the outer conductor 56 and inflow hypotube55 and an inflow channel 17 i formed between the antenna sleeve 2 andthe tapered inflow transition collar 53, the channeled puck 46 and thedistal radiating portion 44. The distal flow channels 70 a-70 d formedby the arrangement of the antenna sleeve stops 68 a-68 d transition thecooling fluid from the inflow channel 17 i formed between the antennasleeve 2 and the distal radiating portion 44 to the outflow channel 17 oformed between the outer surface of the antenna sleeve 2 and the innersurface of the outer jacket 43. Finally, the fluid outflow slots 57 a-57d formed in the outer hypotube 57 directs the cooling fluid from outflowchannel 17 o formed between the EMF shield 28 and the outer jacket 43and an outflow channel 17 o formed between the inflow hypotube 55 andthe outer hypotube 57. As such, the cooling fluid maintains asubstantially coaxial arrangement along the length of the microwaveenergy delivery device 12.

Various structures of the microwave energy delivery device 12 facilitatethe substantially coaxial fluid flow while supporting the coaxialarrangement. For example, the raised portions 66 a of the channeled puck46, the outer taper 60 a of the tapered inflow transition collar 53 andthe distal portions of the antenna sleeve stops 68 a-68 d position theantenna sleeve 2 in substantially coaxial arrangement while forming aportion of the inflow channel 17 i therebetween. Similarly, thesharpened tip 48, the distal portions of the antenna sleeve stops 68a-68 d and the inflow hypotube 55 position the outer jacket 43 insubstantially coaxial arrangement while forming a portion of the outflowchannel 17 o therebetween.

The described embodiments of the present disclosure are intended to beillustrative rather than restrictive, and are not intended to representevery embodiment of the present disclosure. Various modifications andvariations can be made without departing from the spirit or scope of thedisclosure as set forth in the following claims both literally and inequivalents recognized in law.

What is claimed is:
 1. A microwave antenna, comprising: a feedlineincluding a coaxial cable including an inner conductor, an outerconductor, and a dielectric disposed therebetween; a radiating sectionincluding a dipole antenna coupled to the feedline and a trocar coupledto the dipole antenna at a distal end thereof; an inflow hypotubedisposed around the outer conductor, the inflow hypotube configured tosupply fluid to the radiation section; a puck having a first end and asecond end, the puck including at least two ribs extending from thefirst end to the second end defining inflow slots between two adjacentribs; a transition collar having a first end and a second end, the firstend coupled to a distal end of the inflow hypotube and the second endcoupled to the first end of the puck, the transition collar including atleast two outflow slots at a proximal end thereof configured to receivefluid from the distal end of the inflow hypotube and transition thefluid from the at least two outflow slots to a distal end of theradiating section, the transition collar being press-fit over the inflowhypotube and forming a fluid-tight seal therebetween; and a sleeveoverlaying the at least two outflow slots of the transition collar, thepuck and at least the distal portion of the radiating section, thesleeve forming a first fluid-tight seal with the first end of thetransition collar proximal the at least two outflow slots, the sleevedefining a first gap for transitioning the fluid to exit the at leasttwo outflow slots of the transition collar to the distal end of theradiating section.
 2. The microwave antenna according to claim 1,further comprising: an outer jacket surrounding the proximal to distalend of the feedline and forming a fluid-tight seal with one of thetrocar and the distal end of the radiating section, the outer jacketdefining a second gap for receiving fluid from the first gap; and anouter hypotube surrounding the inflow hypotube at the proximal end ofthe feedline and defining a third gap positioned relative to the inflowhypotube, the outer hypotube including at least one slot definedtherein, the outer hypotube forming a fluid-tight seal with the outerjacket proximal the at least one slot, the at least one slot configuredto enable the fluid to flow proximally from the second gap into thethird gap and through the microwave antenna.
 3. The microwave antennaaccording to claim 2, wherein the inflow hypotube and the outer hypotubeare made from stainless steel.
 4. The microwave antenna according toclaim 2, further including a choke configured to at least partiallysurround a proximate portion of the feedline.
 5. The microwave antennaaccording to claim 2, wherein the outer jacket is a non-metalliccomposite thin-walled outer jacket.
 6. The microwave antenna accordingto claim 2, wherein the outer jacket has a wall thickness less than0.010 inches.
 7. The microwave antenna according to claim 2, wherein thepuck is formed by injection molding to form a water-tight seal aroundthe outer conductor.
 8. The microwave antenna according to claim 2,further including a connection hub, the connection hub including: acable connector coupled to the feedline; an inlet fluid port and anoutlet fluid port defined therein; and a bypass tube configured totransition fluid proximate the cable connector to the outlet fluid port.9. The microwave antenna according to claim 8, further including: atleast one inflow tube coupled to the inlet fluid port for supplying thefluid thereto; and at least one outflow tube coupled to the outlet fluidport and in fluid communication with the at least one inflow hypotubefor withdrawing fluid therefrom.
 10. The microwave antenna according toclaim 1, wherein the sleeve is a polyimide sleeve.
 11. A method formanufacturing a microwave antenna, comprising: providing a feedlineincluding a coaxial cable including an inner conductor, an outerconductor, and a dielectric disposed therebetween, the feedline having adistal end and a proximal end; coupling a radiating section to thedistal end of the feedline, the radiating section including a dipoleantenna; coupling a trocar to a distal end of the dipole antenna;disposing an inflow hypotube around the outer conductor, the inflowhypotube configured to supply fluid to the radiating section; disposinga puck around at least a portion of the radiating section having adistal end and a proximal end, the puck including at least twolongitudinal ribs for providing mechanical strength to the microwaveantenna, the at least two ribs extending from the distal end to theproximal end defining inflow slots between two adjacent ribs; disposinga transition collar between a distal end of the inflow hypotube and theproximal end of the puck, the transition collar including at least twooutflow slots configured to receive fluid from the distal end of theinflow hypotube and transition the fluid from the at least two outflowslots to a distal end of the radiating section, the transition collarbeing press-fit over the inflow hypotube; and disposing a sleeve tooverlay the at least two outflow slots of the transition collar, thepuck and at least a distal portion of the radiating section, the sleeveforming a fluid-tight seal with the transition collar proximal the atleast two outflow slots, the sleeve defining a first gap fortransitioning the fluid to exit the at least two outflow slots of thetransition collar to the distal end of the radiating section.
 12. Themethod according to claim 11, further including the steps of: disposingan outer jacket radially outward of the distal end of the feedline, theouter jacket forming a fluid-tight seal with one of the trocar and thedistal end of the radiating section, the outer jacket defining a secondgap for receiving fluid from the first gap; and disposing an outerhypotube radially outward of the inflow hypotube and defining a thirdgap positioned relative to the inflow hypotube, the outer hypotubeincluding at least one slot defined therein, the outer hypotube forminga fluid-tight seal with the outer jacket proximal the at least one slot,the at least one slot configured to enable the fluid to flow proximallyfrom the second gap into the third gap and through the microwaveantenna.
 13. The method according to claim 12, further includingproviding a choke configured to at least partially surround a proximateportion of the feedline.
 14. The method according to claim 12, whereinthe outer jacket is a metallic composite thin-walled outer jacket. 15.The method according to claim 12, wherein the outer jacket has a wallthickness less than 0.010 inches.
 16. The method according to claim 12,wherein the puck forms a water-tight seal around the outer conductor.17. The method according to claim 12, further including coupling aconnection hub to the feedline, the connection hub including: a cableconnector coupled to the feedline, an inlet fluid port and an outletfluid port defined therein; and a bypass tube configured to transitionfluid proximate the cable connector to the outlet fluid port.
 18. Themethod according to claim 12, further including: coupling at least oneinflow tube to the inlet fluid port and inserting the at least oneinflow tube into the inflow hypotube for supplying the fluid thereto;and coupling at least one outflow tube to the outlet fluid port, whereinthe at least one outflow tube is in fluid communication with the secondhypotube for withdrawing fluid therefrom.